Hydrodynamics of UV Laser-Produced Plasma
Abstract
Energy balance, plasma temperature, ablation parameters and asymptotic behavior of ions are measured for plasma produced by laser beams at wavelengths of 0.25 μm and 0.69 μm and pulse lengths of 1 ns to 25 ns with irradiances of 10 ^{10}-10^{14 } W/cm^2. The results are consistent with inverse bremsstrahlung being the dominant absorption process. Energy balance and temperature intensity scaling are in reasonable agreement with analytic and numerical calculations. Scaling laws for the mass ablation rate and ablation pressure from aluminum plasma based on ion diagnostics are obtained at 0.25 μm for intensities ranging from 10 ^{10}-10^{13 } W cm^{-2}. The results are in reasonable agreement with a 1 D steady state ablation model and results from other laboratories. Energy transport measurement for gold plasma indicate the results are consistent with a two region plasma model consisting of a high temperature electron thermal transport region and a low temperature high density radiation transport region. Detailed charge state distributions of the asymptotic plasma measured using a single shot electrodynamic analyzer and comparison with results from a hydrodynamic code that include time dependent ionization and recombination physics are reported for the first time. Reasonable agreement was found between the measured distributions and those calculated by recombination kinetics. However, discrepancies observed in detailed charge state spectrum and partial failure to predict the two peak behavior in aluminum may indicate inaccuracies in the recombination model and failure to include radiation energy transport in the modeling of the aluminum plasma.
- Publication:
-
Ph.D. Thesis
- Pub Date:
- January 1992
- Bibcode:
- 1992PhDT.......112T
- Keywords:
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- UV LASERS;
- Engineering: Electronics and Electrical; Physics: Fluid and Plasma